Long retracting soot blower



Dec. 31, 1968 A, RAUSCH 3,418,680

LONG RETRACTING SOOT BLOWER I Filed April 13, 1967 Sheet 1 of i; Y

INVENTOR.

Dec. 31, 1968 D. A. RAUSCH LONG RETRACTING SOOT BLOWER Filed April 13, 1967 Dec. 31, 1968 D. A. RAUSCH 3,418,680

LONG RETRACTING SOOT BLOWER Filed April 13, 1967 Sheet 3 of 5 in W IN VENTOR.

0X; KS1

1963 D. A. RAUSCH LONG RETRACTINC' 500T BLOWER Dec. 31, 1968 D. A. RAuscH 3,418,680

LONG RETRACTINC- SOOT BLOWER Filed April 13, 1967 I Sheet 5 of 5 INVENTOR.

United States Patent 3,418,680 LONG RETRACTING SOOT BLOWER David A. Rausch, Lancaster, Ohio, assignor to Diamond Power SpecialtyCor-poration, a corporation of Ohio Filed Apr. 13, 1967, Ser. No. 630,741 Iltl Claims. (Cl. -317) ABSTRACT OF THE DISCLOSURE A long retracting type soot blower for cleaning the surfaces of heat exchange apparatuses having a feed tube and a lance tube mounted in telescopic relationship around the feed tube and rotatably and movably carried at one of its ends by a carriage for movement to and from a retracted position and a projected or cleaning position. An auxiliary carriage mounted for movement and drivingly coupled to the principal carriage incorporating a support thereon for movably supporting the lance tube and/or the feed tube in all moved positions thereof and a takeup reel around which a flexible conduit is trained and is maintained in appropriate aligned position for supplying energy to the drive motor on the principal carriage in all moved positions thereof.

BACKGROUND OF THE INVENTION Long retracting type soot blowers of the type to which the present invention is applicable are in widespread commercial use for periodically removing soot, slag and other adherent extraneous deposits from the surfaces of heat exchanger apparatuses to maintain optimum thermal efficiency. In modern high capacity steam generating plants, the increased depth of the tube banks and the pendant type superheater and reheater tube bundles has necessitated increases in the length of the lance tube of long travel type soot blowers in order to obtain complete coverage of the heat exchanger surfaces. The increased length of the feed tube and lance tube to provide for an increased length of travel of the nozzle-end portion of the lance tube has occasioned a gravitational deflection of the lance tube and the feed tube along their unsupported length. Various supporting devices have heretofore been used or proposed for use for preventing the sagging or deflection of the lance tube and feed tube which are disposed in telescopic relationship to minimize binding and wear therebetween.

In addition, the greater travel of the carriage on which the rearward end portion of the lance tube is rotatably mounted has in some instances, occasioned problems or difliculties in the arrangements by which energy is supplied to a reversible drive motor on the carriage for propelling the carriage to and from a retracted and projected position as well as for rotating the lance tube. Various techniques have been employed for providing a simplification of the power transfer conduit which have not been widely adopted in view of one or more deficiencies inherent therein.

There has been, accordingly, an increasing need for a long retracting type soot blower incorporating supporting means for providing adequate support to the longitudinally extending lance tube and/0r feed tube in all moved positions of the principal carriage and for a simplified, durable and reliable device for supplying energy such as electricity or a pressurized fluid to the reversible drive motor on the principal carriage in all moved positions thereof.

SUMMARY OF THE INVENTION The foregoing and other problems and disadvantages of long retracting soot blowers are overcome in accordance with the improved soot blower construction comprising the present invention in which an auxiliary carriage is movably mounted on the frame of the soot blower and is drivingly coupled to and movable in a path adjacent to the longitudinal path of travel of the principal carriage. The auxiliary carriage comprises a framework having a pair of longitudinally spaced rotary members thereon around which a flexible element is trained wherein one flight thereof is connected to the principal carriage and the other flight thereof is connected to the soot blower frame effecting movement of the auxiliary carriage in the same direction in response to and through an increment of one-half the distance of movement of the principal carriage. A supporting bracket is mounted on the framework of the auxiliary carriage which is located in supporting relationship at substantially the midpoint of the unsupported length of the lance tube and/or feed tube in all moved positions of the principal carriage thereby maintaining the lance tube and feed tube in substantial axial telescopic alignment. A second rotary member is mounted on the framework of the auxiliary carriage around which a fiexible supply conduit is trained having one end thereof connected to a junction stationarily mounted on the soot blower frame and the other end thereof connected to the principal carriage for supplying a source of energy to the drive motor thereon. The suppl conduit is maintatined in appropriate longitudinal alignment and in a desired tensioned condition in all moved positions of the carriage preventing any binding or adverse wear of the conduit in response to the reciprocating travel of the carriage.

Brief description of t e drawings The foregoing and other advantages and benefits of the present invention will become apparent upon a reading of the following description of the preferred embodiments of the invention, taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a fragmentary side elevational View of the rearward end portion of a long retracting type soot blower constructed in accordance with the preferred embodiments of the present invention, and with the principal carriage and auxiliary carriage disposed in the fully retracted position;

FIGURE 2 is a fragmentary side elevational view of the forward end portion of the long retracting type soot blower shown in FIGURE 1 with the principal carriage and the auxiliary carriage disposed in the fully projected position;

FIGURE 3 is a transverse sectional view through the soot blower frame illustrating the mounting of the auxiliary carriage and further showing portions of the drive mechanism of the principal carriage in section;

FIGURE 4 is a fragmentary longitudinal sectional view through the soot blower frame illustrating the supports on the auxiliary carriage;

FIGURE 5 is a fragmentary side elevational view of the auxiliary carriage and the drive cable and supply conduit mounted thereon and connected to the principal carriage;

FIGURE 6 is a fragmentary plan view partly in section of the principal carriage; and

FIGURE 7 is a fragmentary horizontal sectional view of the drive system of the principal carriage.

Description of the preferred embodiments Referring now in detail to the drawings and as may be best seen in FIGURES 1-3, a long retracting type soot blower of the type to which the present invention is applicable, comprises a frame 10 of an inverted U-shaped cross section which extends for substantially the entire length of the soot blower. A laterally extending rail 12 of an inverted L-shaped cross section is rigidly aflixed to the left inner side of the frame 10, as viewed in FIG- URE 3, forming a longitudinally extending rail or guideway for movably supporting the left side portion of a principal carriage 14 movably mounted thereon. The right-hand side of the carriage 14, as viewed in FIGURE 3, is supported by means of a support roller 16 which is disposed in rolling bearing contact against the upper surface of a longitudinally extending gear rack 18 which is rigidly afiixed to the right inner surface of the frame 10. Guide rollers 20 aflixed to the upper right-hand portion of the carriage as viewed in FIGURE 3, are adapted to be disposed in rolling bearing contact against the inner surfaces of the frame 10, adjacent to the corner thereof providing for vertical and lateral guidance of the carriage. Similarly, a support roller 24 is adapted to be disposed in rolling bearing contact against the upper surface of the rail 12 on the left-hand side of the frame It), and a guide roller 26 is disposed in rolling bearing contact against the inner surface of the horizontal web of the frame. The rolling bearing contact of the several support and guide rollers against the rails and frame serve to maintain the principal carriage 14 in appropirate longitudinal and transverse guided relationship within the frame 10 while enabling pivoting movement thereof about a transverse axis to permit a small degree of rocking as may be required in response to the deflection of the unsupported length of the lance tube projecting inwardly of a heat exchanger apparatus.

Longitudinal movement of the principal carriage is achieved by means of a drive motor 28 mounted on the carriage and having its output shaft, as best seen in FIG- URES 3, 6 and 7, drivingly coupled to a driven shaft 30 rotatably supported between the ends of a casing 32 in which the carriage gear train is mounted. A pinion gear 34 is affixed to the end of the driven shaft 30 which in turn is disposed in constant meshing relationship with a driven gear 36 afiixed on one end of a shaft 38 having a worm 40 thereon.

The Worm 40 in turn is disposed in constant meshing relationship with a worm wheel 42 as best seen in FIG- URE 3, which is aflixed on a cross shaft 44 on which a pinion gear 46 and a bevel gear 48 are keyed or otherwise rigidly affixed. The pinion gear 46 is disposed in constant meshing relationship with a driven gear 50 mounted on a cross shaft 52 to the end of which a drive gear 54 is afiixed which is disposed in constant meshing relationship with the gear rack 18 on the soot blower frame.

The bevel gear 48, as best seen in FIGURE 7, is disposed in constant meshing relationship with a driven gear 56 which is keyed or otherwise secured to the periphery of a barrel-shaped member or sleeve 58, which is rotatably supported by roller or ball bearings 60 on the carriage casing 32. The longitudinal axis of the sleeve 58 extends substantially parallel to the frame of the soot blower and to the forward or lower end thereof as viewed in FIGURES 6 and 7, a lance tube 62 is adapted to be affixed for rotation therewith and longitudinal movement in response to the travel of the carriage. A feed tube 64 having its rearward end affixed to a supply valve 66 (FIGURE 1), is disposed in stationary sliding relationship within the sleeve 58 and projects forwardly in sliding telescopic relationship within the interior of the lance tube. The feed tube is of a length such that it extends to substantially the forward portion of the frame of the soot blower whereby the end thereof remains in constant communication with the interior of the lance tube for supplying a pressurized blowing medium to the lance tube for discharge through one or a plurality of nozzles (not shown) formed in the forward end portion thereof. A cam actuated lever 68, as shown in FIGURE 1, effects an opening of the supply valve 66 in response to the projecting travel of the carriage and similarly effects a closing of the supply valve when the carriage approaches the retracted or inoperative position to stop the flow of pressurized cleaning fluid to the lance tube before the end thereof retracts inwardly of a wall port in the wall of a heat exchanger apparatus.

It will be apparent from the arrangement of the gear train incorporated within the carriage casing 32 that rotation of the drive motor 28 in one direction effects a concurrent rotation of the sleeve 58 and the lance tube carried thereby in one direction and rotation of the drive pinion 54 against the gear rack 18 whereupon the carriage moves longitudinally of the soot blower frame. Similarly, a reversal in the direction of rotation of the drive motor effects a corresponding reversal in the direction of rotation of the sleeve and lance tube and of the direction of translatory movement of the carriage along the frame. The combined rotation and translation of the lance tube provide for a helical path by which the pressurized blowing medium is discharged from the nozzle in the forward end portion of the lance tube to impinge against the heat exchanger surfaces effecting a dislodgment of soot, slag and other extraneous deposits therefrom. Suitable limit switches such as LSF (FIGURE 2) and LSR (FIGURE 1), can be mounted on the soot blower frame for actuation by the carriage in response to its movement to the forward position and the rearward position so as to effect, respectively, a reversal in the direction of rotation of the drive motor and a deenergization thereof, whereupon the carriage returns to the retracted position and is subsequently deenergized upon a tripping of rear limit switch LSR. The initial energization of the drive motor can be achieved remotely by an operator or automatically in accordance with a preselected operating sequence by a central control system of any one of the types Well known in the art.

The forward end of the lance tube 62, as best in FIG- URE 2, is rotatably and slidably supported by a front roller assembly 70 which is mounted at the forward end of the soot blower adjacent to a wall port 72 which is adapted to be disposed on the wall of a heat exchanger apparatus. The front roller assembly 70 comprises a support bracket 74 which is affixed at its outer end to the upper surface of the frame 10 while its inner end is formed with a bore through which a stud 76 extends in a substantial vertical direction. The lower end of the stud 76 is afiixed to a roller bracket 78 on which a pair of rollers 80 are rotatably mounted and are disposed at an inclination substantially coinciding with the helical path of travel of the periphery of the lance tube during its rotary projecting and retracting travel. A bifurcated member 82 is also affixed to the base or lower end of the stud 76 which is provided with a pair of inwardly projecting screws 84 which are adapted to engage bores on each side surface of the wall port assembly 72 for pivotally connecting these two components to each other. A collar or spacer sleeve 86 is interposed around the stud 76 between the support bracket 74 and the roller bracket 78 which can be adjusted to proper length so that the supporting rollers 80' will be at a proper elevation relative to the lance tube. The collar 86 can be of a length such that the peripheral surface of the rollers 80 effects a small lifting of the lance tube above its normal longitudinal axis so as to compensate for the gravitational defiection of the lance tube when in a fully projected and unsupported condition. Variations in the length of the collar or spacer sleeve 86 does not effect the axial alignment between the supporting rollers 80 and the wall port assembly 72 which are affixed to each other and are raised and lowered in fixed relation.

In accordance with the foregoing construction, it will be apparent that when the principal carriage 14 is in the fully retracted position, as shown in FIGURE 1, the lance tube 62 and the feed tube 64 disposed in telescopic sliding relationship therein extend forwardly of a mountin-g collar 88 affixed to the forward end of the sleeve 58 in unsupported relationship to the front roller assembly 70. Under ordinary conditions the weight of the lance tube and feed tube would efl ect a sagging of the lance tube and feed tube between the mounting collar 88 and the front roller support. Similarly, when the principal carriage is in the fully forward or projected position as shown in FIGURE 2, the feed tube, if of any substantial length, will undergo gravitational deflection due to its unsupported weight between the supply valve 66 and the rearward end of the sleeve 58 in which the forward end portion of the feed tube is slidably supported. The gravitational deflection of the feed tube and the lance tube when the carriage is in the retracted and projected position, as well as during its movement therebetween, has occasioned binding between the feed tube and the sleeve 58 as well as the feed tube within the lance tube in some instances and has also occasioned an increased wear rate of the components. In accordance with the present invention, an auxiliary carriage 90 is provided on which one or more support brackets are incorporated and which auxiliary carriage is mounted so as to move in response to the translatory movement of the principal carriage providing support for the lance tube and/or feed tube at substantially the midpoint of their/its unsupported length.

The auxiliary carriage 90, as shown in the drawing, comprises a longitudinally extending framework 92 which is of a hollow box-shape construction and is connected at its forward end portion to a cross member 94 and at its rearward portion by a cross member 96 which extend laterally thereof to a position adjacent to the opposite sides of the frame. A dolly comprising a bracket 98 having a roller 100 rotatably mounted thereon is removably attached to the forward and rearward end of the frame-work 92. The rollers 100, as best seen in FIGURE 3, are adapted to be disposed in rolling bearing contact against an inwardly turned flange 102 at the lower lefthand portion of the frame forming a longitudinally extending guide rail. Side rollers .104 are rotatably mounted on studs 106 affixed to the upper portion of the framework 92 and are adapted to rotate about a vertical axis whereby the peripheral surface of the side rollers provide longitudinal guidance in response to their rolling contact against the inner surface of the side of the frame 10.

Similarly, a two-roller dolly 108 is aflixed to the end of each of the cross members 94, 96 wherein the rollers 110 thereof are disposed in rolling bearing contact against an inwardly turned flange 112 on the lower edge of the right-hand portion of the frame as viewed in FHGURE 3. Side rollers 114 are mounted on an upstanding bracket 116 providing longitudinal guidance of the auxiliary carriage during its movement along the several rails.

In accordance with a preferred arrangement, the auxiliary carriage 90 is provided with a feed tube support on the cross member 96 and a lance tube support on the cross member 94 which are adapted to be disposed at the midpoint of the unsupported length of these two tubes during all moved positions of the principal carriage. The rear support on the cross member 96, as best seen in FIGURE 4, comprises a roller 118 of an hour-glass con figuration having an arcuate curvature corresponding to the periphery of the feed tube. The roller 118 is supported on a shaft 120 having its ends rotatably supported in bearings 12 2.

The forward support on the cross member 94 for supporting the lance tube comprises a pair of straight rollers 124, as best seen in FIGURES 3 and 4, which are mounted at opposite sides of a U-shaped indentation 126 in the cross member 94 having their shafts i128 oriented at an angle such that the periphery of the rollers 124 corresponds to the helix angle generated by the periphery of the lance tube during its concurrent longitudinal translation and rotation during the projecting and retracting travel.v

The length of the framework 92 and the longitudinal spacing between the cross members 94 and 96 on the auxiliary carriage is such that the rear support roller 118 when the carriage is in the fully retracted position, is disposed in the position as illustrated in FIGURE 1, midway between the supply valve 66 and the rearward end of the rotatable sleeve 58 on the principal carriage. The straight rollers 124 on the cross member 94 when the principal carriage is in a retracted position, are disposed substantially midway between the front roller assembly 70 adjacent to the wall port and the forward end of the mounting collar 88 to which the rearward end of the lance tube is aflixed. As the principal carriage and the lance tube thereon move from the retracted position toward the projected or cleaning position, the auxiliary carriage also moves forwardly but through a distance one-half of that of the principal carriage whereby the auxiliary rear support and auxiliary front support rollers .are at all times disposed in rolling supporting contact at substantially the midpoint of the unsupported length of the feed tube and the lance tube, respectively. During the retracting travel of the principal carriage from the fully projected or cleaning position, the auxiliary carriage similarly moves at a speed one-half the speed of the principal carriage so as to maintain the aforementioned relationship. When the principal carriage and auxiliary carriage attain the fully projected position, the front supporting rollers are disposed in the position as shown in FIGURE 2 at substantially the midpoint of the unsupported distance between the front rollers 80 on the front roller assembly 70 and the forward end of the mounting collar 88 on the principal carriage. It will be apparent from the foregoing in relationship that the longitudinal spacing of the cross member 94 and the cross member 96 and the auxiliary supports thereon, is approximately one-half the distance of travel of the principal carriage.

Coordinated movement of the auxiliary carriage with that of the principal carriage is achieved through a drive mechanism as may be best seen in FIGURES 4 and 5. As illustrated in this drawing, a pair of pulleys or rotary members 130 is mounted in longitudinally spaced relationship on shafts 132 extending transversely through the framework 92. A flexible element 134, such as a cable, is trained around the pulleys 130 and the lower flight 136 thereof is attached to the frame of the soot blower while the upper flight 138 thereof is attached to the principal carriage. In the exemplary embodiment as illustrated in FIGURES 4 and S, the lower flight 136 is split and collars 140 are swaged thereon which are disposed in bearing contact against upstanding ears of a junction bracket 142 which in turn is bolted or otherwise rigidly aflixed to the frame ;10. The upper flight 138 of the cable 134 similarly is split to the ends of which threaded studs 144 are swaged, which in turn extend through suitable bores provided in a bracket 146 attached to the casing of the principal carriage. Lock nuts 148 are threadably disposed on the threaded studs 144 for adjusting the tension applied to the upper and lower flights of the cable. The foregoing pulley and cable arrangement provides a positive mechanical drive connection between the principal carriage and the auxiliary carriage and a drive reduction of one-half, whereby the auxiliary carriage moves in the same direction and at a speed one-half of that of the principal carriage in response to the translatory movement thereof.

In accordance with still another preferred embodiment of the present invention, the conducting means or conduit for supplying energy to the drive motor 28 on the principal carriage is guidably supported on the auxiliary carriage and is maintained in appropriate tensioned and guided relationship in all moved positions of the principal carriage. The term conductor" or power supply conduit is intended to encompass flexible tubes through which pressurized fluids, such as hydraulic oil, or compressed air are transmitted to the hydraulic or pneumatic drive motor as well as electrical conduits for supplying electrical energy to an electrical drive motor as may be desired. The power supply conduit 150, as best seen in FIGURES 4 and 5, comprises a flexible hose of a type suitable for supplying pressurized air to a drive motor of the pneumatic type. One end of the supply conduit 150 is adjustably connected to the junction bracket 142 which, in this instance, comprises a manifold to which the pressurized air is supplied from a central source. As shown in FIGURE 5, the power supply conduit extends forwardly and longitudinally of the framework 92 of the auxiliary carriage and thereafter extends around an idler pulley 152 rotatably mounted on a shaft 154 extending transversely through and afiixed to the box-shaped framework 92. The power supply conduit 150 thereafter extends rearwardly from the idler pulley and has its end connected to a resiliently mounted pipe 156 attached to the depending flange of the bracket 146. A coil spring 158 encircles the rearward portion of the pipe 156 and is disposed in compression against the face surface of the Web of the bracket 146 to maintain the power supply conduit in appropriate tensioned relationship. The other end of the pipe 156, or the outlet end thereof, is connected to a second conduit 160 which, in turn, is directly connected to the drive motor on the principal carriage.

In accordance with the foregoing arrangement, the power supply conduit 150 is maintained in proper tensioned relationship and in alignment with the path of travel of the principal carriage avoiding any sagging or kinking thereof which might otherwise interfere with the uniform flow of air to the drive motor. It will be further noted that in accordance with the power supply arrangement illustrated, a power supply conduit is required which is only approximately one-half the length of travel of the principal carriage. The junction bracket 142, or manifold, is mounted on the soot blower frame at a position approximately at the midpoint thereof and the idler pulley 152 is disposed forwardly thereof as shown in FIGURE 5 when the principal carriage and auxiliary carriage are in the fully retracted position. As the principal carriage moves toward the projected position, the auxiliary carriage moving at a speed one-half of that of the principal carriage, effects forward movement of the idler pulley to maintain the upper and lower flights of the power supply conduit in appropriate longitudinally guided and tensioned relationship. When the principal carriage attains the fully projected position as shown in FIGURE 2, the idler pulley 152 is disposed slightly forwardly thereof in the relationship as illustrated. It will also be appreciated that the idler pulley can be disposed at the opposite end of the framework of the auxiliary carriage with a corresponding reversal in the direction of its upper and lower flights providing a similar guided supply of the r flexible conduit during the translatory movement of the principal carriage.

While it will be apparent that the embodiments of the invention herein disclosed are well calculated to fulfill the objects of the invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. In a long retracting soot blower including, a frame having a carriage movably mounted thereon, a lance tube having one end thereof rotatably mounted on the carriage and the other end adapted to project into a heat exchanger, a feed tube telescopically disposed in communication with the lance tube for supplying a pressurized blowing medium for discharge through a nozzle in the end portion of the lance tube and power means for moving the carriage and lance tube from a retracted and a projected position, the improvement comprising an auxiliary carriage on the frame for supporting one of the tubes during all moved positions of the carriage, said auxiliary carriage comprising an elongated framework, means for mounting said auxiliary carriage on the frame for movement longitutudinally spaced relationship on said framework, flexible means trained around said rotary means having one flight thereof connected to said frame for moving said auxiliary carriage through an increment of one-half the distance and in response to movement of the carriage, and supporting means on said framework disposed in supporting relationship with respect to one of the tubes and movable with said auxiliary carriage to support that one tube at substantially the midpoint of its unsupported length in all moved positions of said carriage.

2. The long retracting soot blower as defined in claim 1, wherein said auxiliary carriage is formed with two supporting means disposed in longitudinally spaced relationship for supporting the feed tube and the lance tube at substantially the midpoint of the unsupported lengths thereof in all moved positions of said carriage.

3. The long retracting soot blower as defined in claim 1, wherein said auxiliary carriage includes a second rotary member on said framework, and a flexible power supply conduit trained around said second rotary member having one end thereof connected to the carriage and the other end thereof stationarily attached to junction means mounted on the frame of the soot blower.

4. The long retracting soot blower as defined in claim 1, wherein the frame is of a hollow rectangular configuration and wherein said auxiliary carriage extends between and is guidably mounted between the inner surfaces of the depending sides of the frame.

5. The long retracting soot blower as defined in claim 3, wherein said power supply conduit is resiliently mounted at one of its ends to said carriage providing for a controlled tensioning thereof in all moved positions of said auxiliary carriage.

6. The long retracting soot blower as defined in claim 1, wherein said rotary means comprise a pair of longitudinally spaced pulleys and said flexible means comprises a cable.

7. The long retracting soot blower as defined in claim 1, wherein said elongated framework comprises a longitudinally extending beam disposed laterally of and in substantial parallel relationship with respect to the path of travel of the carriage.

8. The long retracting soot blower as defined in claim 1, wherein said supporting means comprises a member afiixed to said framework and extending laterally thereof beneath the feed tube, and a roller having a concave peripheral surface disposed in rolling bearing contact with the periphery of the feed tube in all moved positions of said carriage.

9. The long retracting soot blower as defined in claim 1, wherein said supporting means comprises a laterally extending support member aflixed to said framework and disposed beneath the lance tube, and a plurality of rollers rotatably mounted on said support member and disposed in rolling supporting contact with the periphery of the lance tube in all moved positions of the carriage.

10. The long retracting soot blower as defined in claim 1, further includes a support assembly mounted on the forward end portion of the frame for supporting the lance tube at a point adjacent to the wall of a heat exchanger, said support assembly disposed in underlying supporting contact with the lance tube in all moved positions thereof and vertically adjustable relative to the longitudinal axis of the lance tube for compensating for the gravitational deflection of the lance tube when extending inwardly of the heat exchanger.

References Cited UNITED STATES PATENTS 3,195,165 7/1965 Matthews l5317 ROBERT W. MICHELL, Primary Examiner. 

